NEEA/CRHEA/SHS, São Carlos Engineering School, University of São Paulo, São Carlos, SP, Brazil.
NEEA/CRHEA/SHS, São Carlos Engineering School, University of São Paulo, São Carlos, SP, Brazil.
Ecotoxicol Environ Saf. 2019 Oct 30;182:109446. doi: 10.1016/j.ecoenv.2019.109446. Epub 2019 Jul 16.
Increased use of sugarcane pesticides and their destination to non-target environments in Brazil has generated concerns related to the conservation of more vulnerable groups, such as amphibians. Besides the high skin permeability, tadpoles are constantly restricted to small and ephemeral ponds, where exposure to high concentrations of pesticides in agricultural areas is inevitable. This study evaluated chronic effects caused by sub-lethal concentrations of 2,4-dichlorophenoxyacetic acid herbicide on energy storage, development, respiration rates, swimming performance and avoidance behavior of bullfrog tadpoles (Lithobates catesbeianus). Firstly, we conducted acute toxicity test (96 h) to estipulate sub-lethal concentrations of 2,4-D and evaluate the sensitivity of three tadpoles' species to this herbicide. Results showed that Leptodactylus fuscus presented the lowest LC 96 h, 28.81 mg/L, followed by Physalaemus nattereri (143.08 mg/L) and L. catesbeianus (574.52 mg/L). Chronic exposure to 2,4-D (125, 250 and 500 μg/L) delayed metamorphosis and inhibited the growth of tadpoles at concentrations of 125 μg/L. Effects on biochemical reserves showed that 2,4-D increased total hepatic lipids in tadpoles, although some individual lipid classes (e.g. free fatty acids and triglycerides) were reduced. Protein and carbohydrates contents were also impaired by 2,4-D, suggesting a disruption on energy metabolism of amphibians by the herbicide. In addition to biochemical changes, respiration rates and swimming speed were also decreased after chronic exposure to 2,4-D, and these responses appeared to be correlated with the changes detected in the basic energy content. Avoidance test indicated that tadpoles of L. catesbeinus avoided the presence of 2,4-D, however they were unable to detect increasing gradients of the contaminant. Our data showed that chronic exposure to 2,4-D impaired biochemical, physiological and behavioral aspects of tadpoles, which may compromise their health and make them more vulnerable to environmental stressors in natural systems.
巴西对甘蔗杀虫剂的使用增加及其向非目标环境的转移，引发了人们对更脆弱群体（如两栖动物）保护的关注。除了皮肤渗透率高之外，蝌蚪还不断被限制在小而短暂的池塘中，在那里，它们不可避免地会接触到农业区高浓度的杀虫剂。本研究评估了低致死浓度的 2,4-二氯苯氧乙酸除草剂对牛蛙蝌蚪（Lithobates catesbeianus）能量储存、发育、呼吸率、游泳性能和回避行为的慢性影响。首先，我们进行了急性毒性试验（96 小时），以确定 2,4-D 的亚致死浓度，并评估三种蝌蚪对这种除草剂的敏感性。结果表明，Leptodactylus fuscus 的最低 96 小时 LC 值为 28.81mg/L，其次是 Physalaemus nattereri（143.08mg/L）和 L. catesbeianus（574.52mg/L）。慢性暴露于 2,4-D（125、250 和 500μg/L）会延迟变态发育，并在 125μg/L 浓度下抑制蝌蚪生长。对生化储备的影响表明，2,4-D 增加了蝌蚪肝脏中的总脂质，尽管一些个别脂质类（如游离脂肪酸和甘油三酯）减少了。蛋白质和碳水化合物含量也受到 2,4-D 的损害，这表明除草剂会破坏两栖动物的能量代谢。除了生化变化外，慢性暴露于 2,4-D 后呼吸率和游泳速度也降低了，这些反应似乎与基本能量含量检测到的变化有关。回避试验表明，L. catesbeinus 的蝌蚪会回避 2,4-D 的存在，但它们无法检测到污染物浓度的增加梯度。我们的数据表明，慢性暴露于 2,4-D 会损害蝌蚪的生化、生理和行为方面，这可能会损害它们的健康，并使它们在自然系统中更容易受到环境压力的影响。
